Choosing the correct material for a part is a significant step—perhaps the single most important step of the design process. The material chosen will greatly influence the part’s performance, its cosmetic appearance, the cost, and how well the part will mold. Typically, a tremendous effort is put into selecting the correct base resin, as well as its additives, fillers, and reinforcements. Once the ideal material is chosen and the part is molding seamlessly and performing as expected, the work is not yet done. Finding a backup material is the next critical step. Expert engineers will consider this step during the initial design stage.
|Identifying alternative materials for products can avert problems when the original material is discontinued or in short supply. (Image source: The Madison Group)|
What happens if your material supply is suddenly cut off? Do you have a backup material? If so, have you put the alternative material into action to ensure parts can be made with no interruption? Molders are being informed at an accelerated rate that the material they are using will suddenly not be available for the unforeseeable future. This is happening with many different types of resins, from lightly used to very popular ones. This leaves many molders scrambling at the 12th hour to find a replacement to meet their client’s production demands. This article will discuss how this very real situation can be avoided.
A popular credo from motivational speaker Denis Waitley can help molders: “Expect the best, plan for the worst, and prepare to be surprised.” Molders take it in stride when they receive the call that a material is being discontinued or has become unavailable for an extended period of time. These same molders put into practice Waitley’s mantra, “Change the changeable, accept the unchangeable, and remove yourself from the unacceptable.” These molders have another suitable material to substitute at a moment’s notice, as they have previously done the work to verify it as a replacement.
Do you have a plan in place in case you were to receive that call? At the very least, you need to know if there is (or is not) a replacement material for what you are currently using. If you don’t, you are playing Russian roulette with your molding operation. I challenge you to examine some of your most important products and play the “what-if” scenario. Perform a risk management routine when you receive the notice, “We are inflicting a force majeur and your firm will not be receiving xyz material for the indefinite future.” Do not kid yourself. These calls are occurring at what appears to be an increasing rate. Expect a notice like this at some point in your plastics career.
Reasons materials become in short supply or get discontinued:
• The resin manufacturer decides the material is no longer profitable.
• Two resin manufacturers decide to merge. A major reason mergers occur is that someone has decided that major savings can be realized by cutting repeat or similar products. You can also expect that one of the similar products will be cut and a substitute material will be offered.
• Resin manufacturer declares force majeur preventing the fulfillment of the contract. This could be caused by sudden shutdown at the resin manufacturer due to some emergency situation, such as a hurricane, fire, software issue, or logistical issues.
• One or more of the raw ingredients, additives, or fillers the resin manufacturer requires becomes in short supply.
• Planned or unplanned shutdown for plant repair.
Typically, the resin manufacturer or your supplier is going to provide replacements. These options should be weighed heavily. In most cases, you will not be able to simply substitute a new material. Molds are made, and processing conditions are set, for a specific material. If the material needs to be certified to a standard or approved by an agency, such as UL or the FDA, the problem becomes more daunting. If this is the situation, your options for a replacement material are extremely limited, making the need to have a substitute in place even more critical. If you are faced with a material being in short supply or discontinued, it is likely you will need to recertify the part. This could be a torturous process if the material is not UL or FDA certified. Who, then, is responsible for the costs involved with having the material certified under these agencies? It is noted that because the FDA requirements are some of the most stringent, many resin suppliers will explicitly state that the resin can be used for food contact in all countries but the United States.
Identifying alternative materials:
Waitley’s expression, “Expect the best, plan for the worst, and prepare to be surprised,” means that things should be put into place early to ensure that there is a backup material. This is done by the OEM, the molder, or a collaboration of both parties. This process involves many of the steps that were taken when the original material was chosen:
• Review certifications required for the material. If they are required, this is the first place to start because quite a few materials will be eliminated right away.
• Review materials in the same class of the original resin. This will give you the best opportunity to meet the required mechanical properties and moldability.
• Review specific additives, colorants, and reinforcements. Understand why they are in the resin and how they affect the performance of the part (e.g., UV protection).
• Review how the material arrives from the resin manufacturer or supplier. Does it arrive clear, natural, or pre-colored?
• Review how the material is delivered: rail-truck, gaylord, or bag. Make sure your facility has the ability and capacity to accept the material.
• Review material data sheets for properties such as modulus, strength at yield, elongation at yield, elongation at break, melt flow rate (at same conditions), notched izod strength, and density/specific gravity.
• Review multipoint material property data (temperature and time) if available.
• If the part is used at an elevated temperature, it is recommended that the modulus of the material be evaluated over a temperature range via dynamic mechanic analysis (DMA) in order to determine how the stiffness decreases as the temperature increases. Also, test samples following ASTM D 638 “Standard Test Method for Tensile Properties of Plastics.”
• Mold both materials.
• Understand the nuances of molding the alternative material.
• Keep a number of molded “golden standards” for both materials that you can refer to. This will allow you to test a new part to the golden standard properties.
• Determine a method to mark the mold so that you know what material is being molded.
• Ensure that the part with the backup material performs as well as the original material.
• Continue to monitor the availability of the backup material. You want to prevent the situation where you have taken all the necessary steps listed above to only find out that the backup material has been eliminated.
• It is not necessarily recommended that you keep a large amount of backup material in stock. However, it would be excellent planning/foresight if another product being molded in your facility used the backup material. Thus, if something were to occur with either product, you readily have a supply of material, a current source, and you understand how to condition and mold the material, and how the part will behave after molding.
If the material you are molding is cut off and you do not have a backup material, you will likely have to follow the same procedure, but at a more rapid pace. You may expect to be told that there is an immediate substitute. However, this is rarely the case. By using the steps provided above, you can immediately put into place a replacement material and avoid a production interruption.
Molders are more frequently facing the situation where the material they are molding is suddenly cut off with no insight as to when the supply will be continued. This situation is occurring with a wide range of resins. You may expect a substitute material to be recommended, but do not be fooled. This is rarely the case. It is strongly encouraged that you have a backup material identified in which you have full confidence. At the very least, begin to review your most critical parts/resins and start the “what if” scenario.
Paul Gramann is a co-founder (1993) and the president of The Madison Group. He received his Ph.D. from the University of Wisconsin – Madison. He is involved in the design, material behavior, and failure analysis of thermoplastic, elastomeric, and thermoset parts. He also serves on the Underwriters Laboratories Standard Technical Panel addressing polymeric materials (UL 94, UL 746, UL 1694).
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